Trying to understand CH thermostat (and replace with RF)
Dave Liquorice
> The RF thermostats I have in mind are the Danfoss Randall TP5E-RF or
> TP75-RF
Good choice, I have a TP75RF, keeps the temperature within half a
degree C of the one set.
> Q1: What is the 'shunt accelerator heater'?
A resistor to heat the bimetal strip that does the temperature
sensing. If it wasn't there it would take to long for the strip to
warm and the stat would have horrible hysterises. You can safely
ignore it and the neutral connection. The reciver does need live and
neutral to power it along with the live feed for the CH system.
> The RF thermostat I'd like to use includes its own timer. I assume I
> would need to leave the CH timer on all the time (but not the hot
> water), and let the thermostat do the work.
I tried that but due to the noise of CH coming on in the early hours
when it got cold enough decided that this was not a good idea. I know
have the CH programmer set to "all day". The stat looks after the
temperature during the day and it also means that I have an easy way
to decide when the heating is on. The TP75 does have an OFF setting
but you'd have to program that in. Programing the TP75 is easy but not
as easy as selecting OFF on the programmer. B-)
> Q2: Can anyone see any reason (other than perhaps Q1 above) why the
> thermostat I'm proposing to use wouldn't work as a replacement for
> the existing Satchwell one.
None. I was a little concerned about the thick stone walls between the
receiver and transmiter but there doesn't appear to be any problems.
--
Cheers new...@howhill.com
Dave. Remove "spam" for valid email.
Colin M
The "shunt accelerator heater" is to provide hysteresis and prevent the stat
from cycling too quickly close to the desired temperature.
The new stat will provide it's own method of coping with that, so you should
be able to replace it on a like for like basis.
The decode for your pins is :
1 - On
2 - No connection
3 - Live
4 - Neutral
To hook up your new TR1, you'd link the following;
L - Live Supply
N - Neutral
1 - No connection
2 - Link to neutral terminal (common)
3 - On
4 - No connection
Colin
PS It's preferred in newsgoups if you post your images to a website and then
link to the url here rather than attach binary files as these can't be read
by many people.
Dave Liquorice
> To hook up your new TR1, you'd link the following;
RX1 (single channel) or RX2 (two channel) oe RX3 (three channel)
probably with the suffix E now. The UK models are no longer on 418MHz
but 433MHz. Just as well 418 is very prone to problems from TETRA.
> L - Live Supply
OK
> N - Neutral
OK
> 1 - No connection
OK
> 2 - Link to neutral terminal (common)
No I don't think so. I'd connect this to the switched live feed from
the programmer.
> 3 - On
Switched live feed to boiler/pump etc.
> 4 - No connection
Otherwise know as OFF.
Paul Edwards
Just out of interest Dave, where did you get your TP75-RF? I've only managed
to track down suppliers of the TP5E-RF (and then it has to be ordered).
Thanks everyone,
Paul
"Paul Edwards" <ne...@hornist.co.uk> wrote in message
news:Xknv6.48972$g63.6...@nnrp3.clara.net...
> I need to relocate the main thermostat for my CH system. The neatest
option
> would be to replace it completely with a remote RF thermostat. The base
> unit, which does the actual switching, would be sited in my airing
cupboard
> (wired directly into the CH wiring box in place of the existing thermostat
> wires), and the RF remote sensor could then be located anywhere suitable
in
> the house.
>
> Before I plunge in to buying what is a relatively expensive piece of kit,
I
> want to be sure that it's a suitable replacement for my existing
equipment.
> The RF thermostats I have in mind are the Danfoss Randall TP5E-RF or
TP75-RF
> (see http://www.danfoss-randall.co.uk/wiring_8.htm and
> http://www.danfoss-randall.co.uk/radio_controlled_thermostats_lit.htm for
> specs). These provide a straightforward two-way switch (of which I'd only
> use one-way), whereas my existing thermostat seems to use a different
> configuration (see below). I would value any assistance folks can give in
> trying to understand the functionality of the existing thermostat, and in
> determining whether the RF thermostat will work with my system.
>
> The existing thermostat is a Satchwell TLX2259. I've taken the liberty of
> attaching a (very small) GIF file showing the wiring diagram as taken from
> the manufacturer's instruction sheet (easier than trying to draw it with
> line art). As I understand it the live comes in to (3) - which in my case
is
> powered only when the CH timer is on. (1) is then effectively the switched
> live to drive the load only when the room temperature falls below the
> setpoint. What I don't understand is the purpose of the neutral feed to (4
)
> and the item 'c' (which is described in the key as the 'shunt accelerator
> heater'). So here is my first question:
>
> Q1: What is the 'shunt accelerator heater'? Is it something to do with the
> operation of the thermostat, and therefore can be ignored when I replace
the
> thermostat? Or is it something to do with the functioning of the main load
> 'a', and therefore something which any new thermostat I choose must
provide?
>
> Just to confirm how the existing thermostat works on my system I took
> voltage measurements across the terminals using a DVM. The readings I get
> are what I would expect. When the CH timer is not on, there are no
voltages
> present at all. When the timer is on, I get the following readings:
> Thermostat not demanding heat: 1-3 240V, 3-4 240V, 1-4 0V
> Thermostat demanding heat: 1-3 0V, 3-4 240V, 1-4 240V
>
> The RF thermostat I'd like to use includes its own timer. I assume I would
> need to leave the CH timer on all the time (but not the hot water), and
let
> the thermostat do the work. Note that the system doesn't have TRVs. My
> second question is really a more general one (though I appreciate I may
not
> have given enough info to answer it fully)...
>
> Q2: Can anyone see any reason (other than perhaps Q1 above) why the
> thermostat I'm proposing to use wouldn't work as a replacement for the
> existing Satchwell one.
>
>
> Sorry to waffle on, but many thanks in advance for people's help.
>
> Paul Edwards
>
>
> --
> =============================================
> Paul Edwards ne...@hornist.co.uk
> http://www.hornist.co.uk
> =============================================
>
>
>
Dave Liquorice
> Just out of interest Dave, where did you get your TP75-RF? I've only
> managed to track down suppliers of the TP5E-RF (and then it has to
> be ordered).
Special order via Plumb Center. Remember that this is Danfoss so if
you just order a TP75-RF that is all you'll get. You need an RXn (n =
1..3, indicates number of channels) as well. It's not a cheap system,
over £100 but for the features and flexabilty well worth the money.